Reply: ====== * M. Petruzzellis * R. De Blasi * V. Lucivero * M. Sancilio * M. Prontera * A. Tinelli * D.M. Mezzapesa * F. Federico We thank Dr. Fox for his comments concerning our previously published letter to the editor entitled, “Cerebral Aneurysms in a Patient with Osteogenesis Imperfecta and Exon 28 Polymorphism Of *COL1A2*.”1 He strongly informs us of a misunderstanding regarding the de novo aneurysm that developed after 4 months. Dr. Fox points out some potential errors in our diagnosis, claiming that the de novo aneurysm is actually a refilling of the previously treated one. We believe that indeed at 4 months, our images revealed that a new aneurysm had developed in front of the previous one (Fig 2*B*). Further evidence of this was found in the posttreatment un-subtracted images (not published due to space constraints), in which it was possible to appreciate the stent crossing the vertebrobasilar junction and the coils occluding 2 different and clearly separable aneurysms. Finally, we are grateful to Dr. Fox for bringing to our attention some bibliographic references that may help us achieve a better understanding of the anatomic features of this particular case. ## Reference 1. Petruzzellis M, De Blasi R, Lucivero V, et al. **Cerebral aneurysms in a patient with osteogenesis imperfecta and exon 28 polymorphism of *COL1A2*.** AJNR Am J Neuroradiol 2007;28:397–98 [FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiYWpuciI7czo1OiJyZXNpZCI7czo4OiIyOC8zLzM5NyI7czo0OiJhdG9tIjtzOjIzOiIvYWpuci8yOC8xMC8xODQwLjIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) * Copyright © American Society of Neuroradiology